Solid state image sensors, also known as imagers, find applications in a wide variety of fields, including machine vision, robotics, guidance and navigation, automotive applications and consumer products. In many smart image sensors, it is desirable to integrate on chip circuitry to control the image sensor and to perform signal and image processing on the output image. There are a number of different types of semiconductor-based imagers, including charge coupled devices (CCDs) and complementary metal oxide semiconductor (CMOS) imagers. Charge-coupled devices (CCDs), which have been one of the dominant technologies used for image sensors, however, do not easily lend themselves to large scale signal processing and are not easily integrated with complimentary metal oxide semiconductor (CMOS) circuits.
Imagers are typically formed with an array of pixel cells, containing photosensors, such as photodiodes, where each pixel cell produces a signal corresponding to the intensity of light impinging on that pixel cell, when an image is focused on the array. The signals may then be stored and/or processed, for example, to display a corresponding image or otherwise used to provide information about the image.
To detect color and to capture a color image, an absorptive color filter array (CFA) is typically employed and placed on top of the photosensors. For example, each pixel cell may be covered with a respective color filter, such as, for example, a red (R), green (G) or blue (B) filter. In a typical CFA layout, the red, green, and blue filters are arranged in a mosaic sequential pattern, such as a Bayer filter pattern such that the photosensors of the pixel cells separately detect red, green or blue photons.
It is desirable to provide an imager pixel array capable of separating and detecting spectral components of incident light compatible with imager fabrication processes.